


Shadow's NSFW Request Collection

by Shadowinflame



Category: Undertale (Video Game)
Genre: Breeding, Breeding Kink, Cervix Penetration, Come Inflation, Crosstale Sans (Undertale), Crosstale Sans/Dreamtale Nightmare Sans (Undertale), Dreamtale Nightmare Sans (Undertale), Ecto-Body (Undertale), Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Ecto-Tongue (Undertale), Ecto-Vagina (Undertale), Ectobiology, Errortale Sans (Undertale), Knotting, M/M, Nipple Play, Size Difference, Sub Errortale Sans (Undertale), Underswap Sans (Undertale)
Language: English
Status: In-Progress
Published: 2020-12-05
Updated: 2020-12-13
Packaged: 2021-03-09 18:47:47
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,488
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27901000
Author URL: https://archiveofourown.org/users/Shadowinflame/pseuds/Shadowinflame
Summary: Skeletons NSFW. Single warnings will be in the notes of each work
Relationships: Blue/Error, Sans/Sans (Undertale)
Comments: 11
Kudos: 175





	1. ErrorBerry Breeding Kink

**Summary for the Chapter:**

> Requested by shortydegry34 on Twitter

**Notes for the Chapter:**

> Tags/Warnings: Breeding Kink, Cumflation, consensual

Error was the one who invited Blue over to watch Undernovella together but as it was at the moment he wasn't sure anymore if that was a good decision as he hasn't been able to focus on his beloved show for quite a while now.

It had started with Blue just gently hugging one arm around Error, which felt nice and reassuring, telling Error that he wasn't alone. It was a nice feeling, especially knowing the person next to him was Blue and not anyone else. But Blue's hand had slowly travelled down Error's body as the show went on; careful fingers ghosting over his body, tracing Errors ribs through his shirt. Error had gasped the moment they first slid under his clothes but quickly leaned into it, Blue's touch soft and loving, not hurting at all.

Blue hummed a little, leaning closer to Error, hugging his arms around him a little more as his fingers kept exploring below the other's shirt. Not that he would find anything new there, they had seen each other bare-boned quite often, had had intimate moments with each other..

Error noticed his thoughts drifting off to those moments a little too late and it had it's effect on him, his focus shifting away from Undernovella faster then he might have wanted as he gasped a little more audible and a blush formed on his face.

“Is everything alright, Error?”, Blue asked. “I can stop if it bothers you.”

Blue knew that Error wasn't always in the mood for touch and Error appreciated how the other respected his boundaries, always asking, never refusing to stop if it got too overwhelming for him, but.. this time, it wasn't the touch that bothered him, but the thoughts that came with it. Thoughts he couldn't afford to have at a moment that was supposed to be sweet, watching a show together and nothing more.

“I-I'm fine”, Error answered eventually. “D-don't stop, it feels good.”

“Just tell me if it gets too overwhelming and I'll stop”, Blue said and Error's blush just grew in intensity from the love he felt at the caring tone in Blue's voice.

Error nodded in affirmation, then shifted his gaze away from Blue and back to the portal again, trying his best to focus on the show and not the thoughts that were running wild in his mind, screaming at him with every electrifying touch of Blue's gentle hands.

Not that that was really working as he soon found himself back in his thoughts, memories of Blue's hands just a little lover, how the cute, gentle, smiling skeleton he called his partner could get so demanding if he wanted. How he could fulfil all of Error's needs all the while still careful not to go too far. He really loved the other.

Error gasped loudly as his ecto took form, fuelled by nothing but his own thoughts. Blue's hands were still on him, now caressing the newly formed flesh and it took Blue a few seconds to realise what happened.

“Error?”, he asked surprised.

Error's whole face lit up in an embarrassed blush and he didn't know how to explain himself. “I- you, your touch, I-”, he stumbled over his words, not forming any coherent sentences. And yet, even through all the embarrassment he couldn't stop his thighs from rubbing against each other as Blue's hands hadn't left his formed body yet.

“If you wanted us to do it you could've just asked, you know?”, Blue giggled. “No need to miss out on an episode of your favourite show for it.”

“I-it's not like that at all!”, Error protested, glaring at Blue. “I honestly wanted to watch Undernovella with you. It's just..! It's.. the way you were touching me and.. we haven't done it in a while..”

“Oh, so that's how it is”, Blue smiled and kneeled down in front of the sofa they sat on, facing Error. He hummed a little while his fingers played with the hem of Error's pants, caressing the little bits of the other's pelvis that were exposed. “If that's what you want.. well, who would I be to deny such a request from you?” he whispered and finally pulled Error's pants off, the other willingly lifting his hips to help.

Blue couldn't help the smile that spread over his face at the sight in front of him. He had never before seen Error get this wet without Blue directly touching the other. He immediately rubbed both his thumbs over the other's folds, gathering the slick wetness that seemed to almost drip from Error's pussy, spreading it up to Error's clit with one thumb while the other circled around his lover's entrance.

Error whimpered, finally getting the touch his mind had been imitating for him earlier and he couldn't stop himself as his hips just jerked forward, meeting Blue's thumb as he was just about to press in.

Blue gasped in surprise as his thumb went all the way in and a moan escaped Error. Even though he always waited for the other's consent, it was rare to see Error allow his body to move freely, always still a little stiff even though they had done this more than once by now. This was a nice change, though he wondered if Error even realized what he was doing.

Either way, that wouldn't stop Blue from giving him the pleasure he asked for. He moved the other thumb down to Error's pussy as well, spreading it open wide enough to thrust three fingers in. It was enough to fill Error out and Blue knew he had to prepare him a little more before he went in himself.

Error covered his mouth with both hands to suppress another moan as Blue started to move his fingers in and out of him. He was so wet already, he wanted his lover now but he was still too embarrassed to let the words slip past him.

Blue didn't like it. “Don't cover your mouth, let me hear you”, he cooed and his fingers slipped out of Error again to take both his hands and move them away from his mouth. Then he leaned down to kiss the other, soft at first, but growing rough and demanding after a few seconds as he let one hand travel back down between Error's legs, rubbing his clit.

Error moaned into the kiss and it echoed through all of the Antivoid as Blue pulled away. The Underswap skeleton grinned, satisfied with the noises he could pull from his lover and pushed his fingers back into Error's pussy, stretching him further.

Error moaned and squirmed under Blue's touch, desperately trying to get more of him, his hips were jerking up as every touch send a burning pleasure through his whole body. His body was growing hotter by the minute, longing for Blue to fill him up and his fingers started twitching, urging him to do something with them. But he didn't, keeping them to his sides and allowing Blue to take control.  
Which he gladly did, finally pulling his own pants down to release his erection. “I'll know what you're yearning for”, he said with a shaky breath and rubbed his dick against Error's folds for a moment, getting it all nice and slick before he finally pushed it in. “I'll fuck you until you can't walk anymore, mark you so everyone knows you're mine”, Blue whispered next to Error's ear.

Words did so much to him and Error moaned loudly, not even attempting to cover his mouth this time and that was all Blue needed. He started moving immediately, starting out with slow but rough thrusts, getting deeper with each one until his dick was completely buried inside of Error. With both hands he lifted Error's legs up over his shoulders and leaned down to kiss Error again.

He pulled away shortly after, his tongue trailing along Error's jaw and neck as he started thrusting into the other. It didn't take him long to find an angle that had Error screaming, his hips jolting forward to meet Blue's intruding length. Blue moaned loudly and grabbed both of Error's hands, holding them to the backrest of the sofa and squeezing them tightly. Error squeezed back, glad Blue was holding his hands as his legs slipped off the other's shoulders and down to his waist. Error wrapped them around Blue's waist, pulling him even closer, falling into the fast rhythm the other had picked up. 

The next hard thrust from Blue had Error arche his back far enough for his head to lean on the backrest. "O-oh stars, Blue!", he moaned.

Blue just groaned, acknowledging he hear Error.

"D-don't s-stop", Error moaned. "F-fill me up, fuck me pregnant! Please! Blue!"

Blue moaned and only increased the pace in which he fucked Error as he felt the other clench around his dick like it was the only thing to hold onto.

"You feel amazing", he breathed and he could feel a shudder going through Error's whole body. "The way you're clenching around me, I can never get enough of it! But you'd feel even better with your pussy dripping wet with my magic so I'll make sure to cum inside of you."

Error couldn't help but clench around Blue even tighter at that, the words of his lover only forcing more of his own magic to pool down and collect at his pelvis. 

Lost in pleasure, he barely realized it as Blue let go of his hands to grab his hips. The Underswap skeleton would always make use of his extraordinary strength in the most unexpected of moments, Error knew that and yet he was surprised as Blue suddenly picked him up, still fucking into him as he stood up to change their positions, sitting back down with Error now on top of him.

After he overcame the initial surprise Error lifted his hands to Blue's shoulders, stabilizing himself enough to lift himself up a little, then sink back down. He had never been really good with this position, but Blue was more then willing to help him out. Error moaned as he felt Blue's phalanges dig into the soft flesh of his ass, spreading both his holes apart while he lifted Error up, allowing his own hips to jerk up into the dark skeleton while he pushed him back down. 

Error screamed in pleasure as this position only allowed Blue to reach even deeper into him, filling him up more. Tears of pleasure started to form in his sockets as he eagerly followed the movement of Blue's hands, daring the other to lift him a little higher, push him down a little harder.

His hands started to tremble and gave up eventually and he had to resort to hugging Blue instead, leaning his head on the other's shoulder. But he refused to stop there, his hips still moving up and down, without the help of Blue's hands even, while Error spilled breathless moans between gasps for air.

“You have absolutely no stamina”, Blue laughed and lifted the panting skeleton off him, turning Error around to press his chest against the backrest of the sofa, entering his dripping pussy from behind. “But it's fine, that's what you got me for, anyway. Don't you worry, love, I'll take good care of you.”

Error wanted to say something, a week protesting noise escaping him before Blue turned his head around to kiss him again, demanding tongue pressing into his mouth, taking even the last breath out of him. But Error gladly granted him entrance, his multiple tongues immediately wrapping around Blue's, savouring the sweet taste of the other. Blue's tongue, strong as he was, easily wrestled free from the hold Error's tongues had on it, eagerly toying with every one of them while one of his hands once again went down to touch Error's clit.

Error felt himself get light-headed at the lack of air but it only fuelled his desire for the other even more. As soon as he felt Blue pull away from his mouth he wrung for air, taking in huge gasps while his body shook. The way Blue was frantically rubbing his clit told him the other was about as close as he was and oh, how much he wanted him right now.

“Are you close, Error?”, Blue asked, voice sugary sweet and teasing.

“Blue”, Error panted. “S-stars, Blue, you know I am! Come on, don't make me wait for it!”

“Oh, I'll fill you up good, Error”, Blue hummed. “I'll make sure to get you pregnant this time. Screw your messed up code, you'll have my children eventually!”

“Just give it to me already, fill me up, dammit!”, Error screamed, clenching around Blue even tighter as he forcefully rocked back one last time. “C-cum inside of me, Blue!”

Blue screamed Error's name as he finally came, hot cum spilling into Error's formed stomach. Just the feeling of the hot magic flowing into him and the thought of even the smallest possibility of a child forming out of it pushed Error to the edge as well and he came, voice glitching as he tried to form Blue's name. 

Error was still trying to calm down from his high as he felt his stomach press against the backrest of the sofa and he looked down. Blue was still buried balls deep inside of him, spilling his magic load into Error's stomach which was stretching outwards to accommodate. 

Blue reached around to touch Error's stomach, caressing the now obvious bulge and Error whimpered slightly. “B-blue.”

“Told you”, Blue whispered with a slight chuckle, “I'd get you pregnant one way or another.”

“You've got a lot to give”, Error panted and leaned back as far as he could to look at his lover.

“And you're taking all of it so perfectly well”, Blue smiled an then leaned down to kiss him. “I love you so much, Error.”

“Love you too”, Error mumbled, exhaustion starting to take over. “I should invite you over more often.”

Blue just chuckled as he finally pulled out of Error and hugged the other, sitting back down on the sofa with him. “Next time you can just tell me what you want so you don't have to miss out on Undernovella though”, he giggled.

Error hummed in agreement.


	2. Crossmare Nippleplay and Knotting

**Summary for the Chapter:**

> Requested by Neah on Twitter

**Notes for the Chapter:**

> Tags/Warnings: Knotting, Nippleplay, Size Difference, Cervix Penetration, consensual

“Well, that was successful”, Nightmare said as he walked out of the shop again, closely followed by Cross. “You're getting better every time, I think these solo-sessions are really paying off.”

“You've been very patient with me, Boss”, Cross answered, expecting Nightmare to just open a portal to get them out of the AU they were in.

But Nightmare seemed to have other plans. His eye fell onto the now empty inn that was next to the store they had successfully emptied of any useful items and he walked towards it.

By now Cross knew better than to question Nightmare so he followed him wordlessly. He had expected that Nightmare might want to take the money off the counter like they did in the store before, but he didn't. Instead, Nightmare walked up the stairs to where the rooms were located, then entered one, waiting for Cross to come in as well.

“Working with you is always such a pleasure”, Nightmare cooed as he closed the door behind both of them. “And good work needs to be rewarded, am I right?”

Cross swallowed back any attempt at an answer as Nightmare walked in front of him again, the other's clothes already filled out with his ecto, big breasts filling out Nightmare's sweater perfectly. 

“I asked you a question”, Nightmare stated while he shrugged his jacket off, placing it on the nearest chair. “If you don't want your reward though, we can just go back to the castle this instant.”

“Y-yes, I mean no- I.. I mean I would like a reward, B-boss”, Cross stuttered, trying to look at Nightmare, but his eyes kept trailing off, fixated on what he knew was under that tightly filled sweater.

“I know I'm small”, Nightmare huffed, “but I'm pretty sure my eyes are a little higher, Cross.”

“I- am aware, s-sorry Boss.”

“Well, I don't really care”, Nightmare sang as he pulled his sweater off, throwing it to the jacket on the chair and sitting down on the only bed in the room “As long as your eyes are on me that's enough. I'm a little exhausted, but I'm sure that's no problem. You are free to do whatever you want, my body is yours for now.” While he was talking Nightmare lay down on the bed, cushioning himself with his tentacles to get comfortable.

Cross gulped, that was an offer he couldn't possibly say no to. So he moved over to the bed slowly, his magic already pooling to his pelvis before he even touched the other. Nightmare looked so hot sprawled out on the bed like this, his lush breasts freed from all clothes and just begging for Cross to wrap his hands around them. 

Cross breathed in shakily as he finally kneeled down on the bed, legs on either side of Nightmare's. Never before had the other just offered himself up like this and Cross was wondering if this was just another test. Even if it wasn't, he wanted to pass so he reached his hands out and started to softly caress the other's mounds.

Nightmare let out a soft hum which Cross took as a sign of the other feeling good. Knowing he was the cause of it motivated Cross enough to grab Nightmare's breasts just a little harder, fingers rubbing over the other's inverted nipples in hope of teasing them out of hiding. Pretty soon he felt one of the cute little buds between his fingers, but he wanted both and he wanted them now so he leaned down, licking all over Nightmare's breast before he wrapped his mouth around the still inverted nipple and started sucking, all while his other hand never stopped pinching and tugging at the already exposed one.

Nightmare pressed his eye shut as a loud moan escaped him and moments later Cross felt the smaller one's nipple on his tongue. He smiled satisfied and twirled his tongue around it for a moment before he pulled his mouth away from the nipple again, blowing cold air over the wet spot. 

Nightmare shivered for a second before the feeling of Cross' teeth on his opposite nipple drew a scream from him that quickly turned into a moan and his back arched upwards into the other's touch. 

As Cross looked up and saw the other's mouth still slightly open he couldn't help but lean in, pressing their teeth together. He was startled for a moment when he felt Nightmare actually kiss back, though he broke out of it quick enough and lifted Nightmare up with one hand, all while the other was still tweaking and twirling the other's nipples.

The slight shift in their positions caused both their pelvis to rub against each other and Nightmare was able to feel the large bulge in Cross' pants. He moved his hips up against it and smiled as Cross broke the kiss, gasping in surprise. 

Cross dared to glance down briefly and the obvious glow in both their pants made him stop all his movements.

Nightmare chuckled. “What 's the hold-up?”

“I-”

“Come on, I told you you are free to do whatever you want”, he rasped, guiding Cross' hands down to the waistband of his pants “Better use this chance, soldier, you might not get a second one.”

Cross' fingers were trembling as he hooked them into Nightmare's waistband, he still couldn't believe the other would allow him to go this far. But Nightmare arched his back and hips upwards the moment Cross pulled on the pants, helping him to get them off. 

With precise movements Cross threw the pants to the rest of Nightmare's clothes on the chair, then looked his Boss up and down. The other was dripping wet already – from his breasts alone. Though it had a similar effect on Cross, rock hard dick uncomfortably pressing against his pants just inches above Nightmare's soaked pussy.

Cross sat back on his knees and slowly let his hands move down Nightmare's sides until he reached his thighs. He gently rubbed small circles on their inside with his thumbs, reaching just a little higher every few seconds. Above him Nightmare squirmed and whimpered, impatiently spreading his legs apart a little more. His hips jolted forward the moment Cross finally reached his pussy and spread his folds apart with his thumbs.

“S-stop teasing”, Nightmare panted and softly smacked Cross on the head with a tentacle while another one tugged on the soldier's waistband. Finally Cross' dick sprung out of his pants and both of them gasped. “F-fuck”, Nightmare mumbled and he felt himself get wetter just at the sight of the other's dick. “Someone's got a lot to give.” 

Cross was long enough to deeply wreck his insides and the knot – Nightmare's tentacles pushed and shoved on Cross' back, one of them angling his dick right in front of Nightmare's entrance. 

Cross weakly protested, mumbling things like Nightmare not being prepared enough and that he was going to hurt the other and Nightmare sighed. He pushed his hips down and the tip of Cross' dick slipped in easily making both of them cry out in pleasure. 

“Don't make me wait”, Nightmare mumbled and his demanding tone broke something loose inside of Cross.

Cross grabbed Nightmare's hips like a lifeline and started to push in. He groaned as he could see his purple dick move inside of the other through his cyan ecto and let out a small moan as he watched Nightmare's stomach start to bulge outwards, eagerly taking all of his thick length. 

Nightmare followed Cross' gaze and saw what had the other so mesmerized. He reached down with one hand, touching the other's dick through his own ecto and his insides clenched around it. Cross was in up to the knot now and Nightmare felt so perfectly full, he needed the other to- 

“Move, Cross, now!”, he screamed out and he hated how he almost sounded desperate.

But all that was forgotten the moment Cross pulled out of him slightly just to thrust back into him, falling into a steady rhythm almost immediately, the head of his dick hitting Nightmare's cervix with every other thrust.

“Oh fuck Cross”, Nightmare moaned, his head pressed deep into the pillows below him. “S-so deep.”

Cross groaned, Nightmare was so tight, his walls basically sucking Cross back in every time, accepting everything Cross was giving him. And the sounds the other made! Cross had never believed his Boss would be capable of such sweet moans, so used to the harsh and demanding tone of the other. This was a whole new experience and he would make sure to savour it.

And the first step to doing so was making sure he'd hear more of the other's voice that had changed only for this occasion. He reached one hand down to Nightmare's pussy again, gathering some of their mixed fluids before smearing it over the other's clit, stimulating the small bundle of nerves. It drew a yelp from Nightmare that quickly became a moan as his hips jerked down, forcing Cross' fingers to rub him some more.

Cross loved it, loved the other's voice and loved seeing and hearing the effect his hands had on Nightmare. And he loved those big breasts that were bouncing up and down with every thrust, those nipples that came out of hiding just for him. He reached up with his other hand, cupping one of those beautiful mounds again, teasing the nipple between his fingers.

Nightmare let out a small squeak followed by a breathless moan and every one of his limbs suddenly wrapped around Cross, tugging him closer, rubbing their bodies together, sharing the heat of their ectos. And suddenly Cross found his face hovering over Nightmare's and he slowed down for a moment to study the other, flushed cyan down to his neck, eye pressed shut and mouth slightly parted in pleasure – he was basically begging for Cross to lean down those few last inches, kissing the other's open mouth, pushing his tongue in where it was eagerly greeted by Nightmare's own.

The movement of their tongues against each other was just as frantic as their hips thrusting together. It was a heated fight – not for dominance but for touch – both trying to get as much from the other as they were giving.

But it wasn't enough, not close enough, the connection not deep enough yet. So Cross gripped Nightmare's hips again, a little tighter this time. He broke the kiss and started turning the other around while still buried deep inside of him. Nightmare yelped in surprise, his tentacles letting go of Cross to support his trembling legs as he was moved to kneel on the bed.

As soon as Nightmare managed to stabilize his position on the bed again he pushed himself up with his arms and started thrusting back against Cross again.

Nightmare barely heard the wet sound of Cross' hips slapping against his own, but he sure felt the other's dick slip into his cervix and that did it for him. He came with a loud scream of Cross' name, his arms trembling as his vision went black for a moment. He felt Cross' arms around himself though and leaned into the other.

Cross hugged Nightmare to himself a little closer, still attempting to thrust into him despite being deeply knotted inside of the smaller one's pussy. He reached up to squeeze Nightmare's breasts again and the soft sounds that came from him finally pushed Cross over the edge as well. 

He was seated deep enough in the other for his cum to spill directly into Nightmare's womb and he already feared whatever his Boss would tell him once he realised. But for now Nightmare only threw his head back against Cross' chest, moaning and whining the other's name while his insides milked Cross for even the last drop.

As his high let up Cross collapsed onto the bed together with Nightmare, waiting for his knot to calm down enough for him to pull out of the other.

Nightmare was panting and holding his stomach, not even trying to turn around and face his subordinate as he said: “We can't go back like this. I expect you to take good care of the mess you made of me in the bathroom over there as soon as you're out of me.”

He vaguely pointed to a door with one of his tentacles and Cross just hummed in agreement, more than happy to be able to touch Nightmare some more, even if it was just to clean him up.


End file.
